1. Field of the Invention
The present invention relates, in general, to integrated circuit (IC) systems, and, more particularly, to a self-configuring multiple IC system having a device performance signature stored in at least one chip.
2. Relevant Background
Great advances in various fields of electronics have been achieved by increasing the level of integration of components to form systems on integrated circuit (IC) chips. Increasingly, IC chips are optimized to perform a specific application while also trying to minimize the number of external components and the cost of the IC.
While it is generally desirable to integrate as much if not all system functionality on a single IC, this is often impractical. Particularly where the functions performed by various parts of the system are quite different, and require disparate or incompatible IC fabrication technologies. Quite frequently, for example, a system requires a certain degree of logic, intelligence or programmability while at the same time requiring specialized devices to monitor, sense, or drive external devices. Quite often systems have comprised an interaction between analog/linear subsystems used to acquire and/or generate analog signals and digital subsystems that are more suited for processing and storing binary data. The overall tradeoffs between system performance and cost can be improved by implementing the system using two or more separate ICs.
One example of such a system is a power current driver used to drive power or high current devices. Such systems include power switches that are designed to handle relatively high current loads required to drive motor coils, switching regulator coils, read/write heads in disk drives, and the like. In such systems the technology used to manufacture the power switching devices such as power bipolar and double diffused metal oxide semiconductor (DMOS), is difficult to integrate with the processes used to manufacture control logic devices, such as complementary MOS (CMOS) technology. Moreover, power switching devices are typically designed to operate at high temperatures where conventional CMOS devices may perform poorly. Although a variety of attempts have been made to integrate power switching and logic devices, these integrations still remain an expensive solution.
As a result, typical systems are formed using two or more chips such that one device implements the power switching functions and another chip implements the control logic that drives the power switch. The control logic is typically implemented as an application specific integrated circuit (IC) having programmable logic, memory, and data or signal processing capability integrated on chip. In this manner, each chip can be manufactured using processes that improve their respective performance without compromising performance of the other chips in the system. Further, a single control chip design can service a wide range of applications with programming changes, and upgrades to either chip can be made independent of the other chip. These advantages greatly favor multi-chip designs.
In contrast to the driver example above, there are many applications that involve a linear chip that provides input to a logic device. The field of sensors, such as optical, chemical, pressure, acceleration, electromagnetic fields and the like are one example of multi-chip systems. Sensing devices themselves often require very specialized manufacturing techniques and packaging that are incompatible with logic and digital signal processing systems used to drive and monitor the sensors. Similarly, radio frequency and microwave frequency devices that are used in transmitters, receivers, and amplifiers often are implemented in separate chips from the logic devices that are used to process the received and transmitted information.
Analog or linear devices are typically specified to operate within relatively wide ranges of performance parameters. For example, a power transistor is characterized by several critical parameters such as on resistance, input capacitance, temperature sensitivity, rise/fall time and the like. Sensors may specify output linearity and temperature sensitivity. Transmitter and receiver circuits may provide a particular output and/or input impedance that affect their performance. Each device is tested to fall within a specified range of parameters for each characteristic. As a general rule, the wider the range of parameters that can be accepted, the lower the cost of the devices. Conversely, devices with very narrow parameter ranges tend to be exceptionally expensive.
As a result, system designers often detune a particular design to allow wide parametric ranges that will be encountered in mass production. Moreover, because designers do not have actual knowledge of the parameters for a particular system implementation, designers typically add guardbands around the specified parameters to ensure operation under all expected conditions.
As an example, in a motor control circuit the timing of the drive signal applied to the power switch is dependent upon the input capacitance, switching speed, and on resistance of the power switch. A large input capacitance requires more drive current supplied by a control chip as compared to a switching device with a lower input capacitance. Because the system is designed to perform with a wide range of input capacitance, however, the control circuit may be configured to supply a single large current that will ensure the worst-case power switch is driven to switch in an acceptable time. However, the system designer could specify much better performance, with no changes in components, if only the designer knew precisely what input capacitance was to be driven.
In the motor control example this compromise will affect how tightly the motor's response can be specified. If the motor control circuit is used in a disk drive, for example, the result might be significantly lower storage capacity or significantly higher access time for a given set of components than is actually possible. Conversely, a disk drive of a given performance could be manufactured using less expensive motor control parts if only it were possible to efficiently performance tune the multi-chip systems.
Fine-tuning multi-chip systems is often expensive or impossible. Temperature compensation in sensors, for example, may require complex laser trim operations performed before device packaging. Alternatively, a companion IC can be programmed to provide compensation of the output signal, but this requires that the companion IC be trained and programmed once the system is assembled. In many cases, critical parameters cannot be measured after packaging, in which cases performance tuning is impossible or incomplete.
Hence, a need exists for systems, methods, and devices that enable performance tuning in multi-chip electronic systems. Moreover, a need exists for systems that enable more efficient use of devices having wide ranges of performance characteristics. Further, systems and methods for automatically performance tuning multi-chip systems are needed.